A fiber cleaver is a device for cleaving optical fibers. Usually it comprises an upper cover and a base, wherein the base is provided with a guide rail framework capable of moving back and forth; a blade is arranged in the guide rail framework; during cleaving, the fibers to be cut are horizontally placed and perpendicular to the direction that the guide rail framework moves back and forth, to cause the guide rail framework to move, and the blade passes through the fibers to be cut and forms a notch on the fibers, so that the fibers are cut off. Patent CN201220240985.1 discloses a fiber cleaver which has a carrying case, main body, and a movable unit with a blade member, and the movable unit with a blade member comprises a blade holder and a blade member mounted to the blade holder and forming a scratch on a glass fiber portion of the fiber, and the movable unit with the blade member is provided on the main body. Among others, the main body utilizes the movement of the blade holder to move the blade holder from the cleaving preparation position to the initial position by the elastic force of the spring, however, the force of the bounce is unstable when the spring is used for the cleaver, and the force of the spring is attenuated along with the increase of the service life, so that the end face of the fiber is easy to be cut unevenly, resulting in cleaving failure, and the fiber needs to be reprepared and recleaved. This reduces the utilization rate of the fiber and causes waste of the fiber, thereby increasing the cost, reducing the production efficiency and bringing a lot of inconvenience to the operator.